1. Field of the Invention
The present invention relates generally to network links and, more particularly, to exchanging channel, physical layer and data layer information and capabilities.
2. Introduction
Physical layer devices are designed to communicate over a communication channel, which can include physical media such as twisted pair cabling, fiber optics cabling, coaxial cabling, etc. The characteristics of the communication channel are significant in its impact on the ability of the physical layer devices to support various link speeds and various types of network services.
As is well known, the characteristics of the communication channel are a key determinant in identifying a link speed at which the physical layer devices can operate. Consider for example, communication over twisted pair cabling. Various communication channel characteristics over twisted pair cabling have been defined through the various Ethernet cable types, such as Category 3, 5, 5e, 6, 6A, 7, 7A, etc. Ethernet cabling. Each of these Ethernet cable types define a particular level of communication channel characteristics, which can correspondingly support different levels of transmission performance.
For example, Category 3 unshielded twisted pair cabling enables 10BASE-T transmission but not 100 BASE-TX transmission, which requires communication channel characteristics exhibited by Category 5 cabling. Category 6 cabling has since been defined and can support 1000 BASE-T operation as well as limited reach for 10 GBASE-T. Still further, advanced Category 6A, 7, and 7A cabling types have been defined for 10 GBASE-T, with Category 7A cabling and beyond likely supporting speeds of 40 G and beyond. In general, the transmission rate on a link, or more generally the delivery of services on a link, is dependent on the ability to take advantage of physical layer properties associated with the connected devices and the communication channel characteristics (e.g., type of cabling, length of cabling, connectors, etc). What is needed therefore is a mechanism that enables the devices to coordinate their channel, physical layer, and data layer information and capabilities to deliver network services efficiently.